Nice build for the budget minded consumer. The i3 does have hyperthreading which does help in some games. It has the haswell processor so if you'd like to upgrade you can bump up to an i5 or even an i7. The graphics card is a little weak, but it should get you 1920x1080 on mid-high settings. You've got plenty of room to upgrade ram later on as well, should you decide to get 4gb more later on.
Another thing you might note, PC Partpicker doesn't have all shipping costs listed, so some of those prices may be cheaper once you click the links. For instance, Windows 7 through NCIX ($84) is cheaper listed, but they don't list a shipping price on PCPP. Newegg ($89) has free shipping on windows, where as NCIX costs 7 bucks more after shipping.
the build by ScrewySqrl is much better for $600 an i3 and worst a 650 wont get you anywhere u might like nvida cause it sound cool but its just more expensive first build is much better.ul end up paying 600 for something a 400ps4 can beat.
and with a 650 u wont be playing anything on high in 2014(might do medium with low fps)
The issue with your view point is not figuring upgrade-ability. This console can easily be upgraded to an i5 or i7 and the 650 ti is quite a capable card for mid-high settings, also with the chance to upgrade. Dual 650 ti can keep up with most games nowadays on high-ultra, I should know i have 2 friends that use them daily for crysis and skyrim.